1. Field of the Invention
The present invention relates generally to vertical processing vessels which are commonly referred to as shaft or vertical kilns, shaft furnaces or shaft generators depending upon the process for which the vessel is being used and more particularly to a new and improved feed hopper, particle separator, fluid distributor and removal grate for use in such vessels.
2. Description of the Prior Art
A common form of processing equipment found in diverse industrial applications is a vertical vessel having a gravity flow of particulate solids from an upper feed to a lower discharge. Commonly, such vessels are called shaft or vertical kilns, shaft furnaces, shaft generators and the like depending upon the application and particular type of material being treated. Such vessels have been found useful for burning or calcining treatments such as the calcining of various types of materials to produce lime, coking coal, burning magnesite and/or dolomite, retorting oil shale, etc. Such vessels commonly include a vertical vessel shell, means for uniformly feeding granular or pulverulent material across the lateral extent of the vessel, a lower discharge means for providing a uniform discharge of the solid material from the vessel shell and some means for introducing treating fluids into the solids so that the solid material is treated in accordance with the pre-designed process. One of the major problems encountered in this type of vessel is the requirement for the uniform flow of solids across the lateral extent of the vessel from its top to its bottom so as to provide uniform treatment of all the solid particles passing through the vessel. Another problem is the uniform lateral distribution of the treating fluid, again to provide uniform treatment of the particles passing through the vessel.
In order to accommodate the above problems, many such vessels are rectangular in cross-section as it is easier to uniformly distribute fluids across a four-sided cross-section. Some vessels are circular in cross-section, but it is difficult to control uniform movement of the particulate material through the vessels as well as being difficult to control the uniform distribution of the treating fluids through the vessel.
The need to uniformly distribute the particles across the lateral cross-section of the vessel is important due to the fact that the material being processed typically is crushed and therefore is presented in a variety of sizes which are fed through the top of the vessel. The particles are typically centrally fed to the top of the vessel, and a certain amount of segregation automatically occurs with the larger particles usually migrating to the periphery of the vessel while the smaller particles concentrate near the center of the vessel. This is due to the natural angle of repose of the material as it accumulates in a feed hopper.
A similar situation typically arises with the counterflow of treating fluids as they will follow a path of least resistance which is naturally through the larger particles. Since the larger particles tend to congregate along the perimeter of the vessel, the counterflowing fluids tend to channel along the side walls so that a uniform exposure of the particulate matter to the treating fluids is difficult to obtain.
There are several features of a vessel that have an effect on the flow patterns of the particulate matter through the vessel as well as the treating fluids. As mentioned previously, as material is centrally deposited into a vessel, the larger particles tend to migrate radially outwardly at a faster rate than the smaller particles, and accordingly, systems have been developed for introducing the particulate matter to the vessel in a manner to avoid this known phenomenon of segregation. An example of such a system is disclosed in U.S. Pat. No. 3,071,230 issued to Brakel, et al. on Jan. 1, 1963. This patent uniformly distributes the inflowing particulate matter across the lateral cross-section of vessel to minimize the angle of repose problem.
It will also be appreciated that if the material is not removed from the bottom of the vessel in a substantially uniform cross-sectional manner, the flow rate of the particulate matter through the vessel will vary aoross the cross-section of the vessel. Accordingly, systems have been developed and employed for removing the particulate matter from the bottom of the vessel in as uniform a manner as possible, so as to maintain a uniform cross-sectional flow of the particulate matter through the vessel. Examples of such devices for regulating the uniform withdrawal of particulate material from the vessel are shown in my U.S. Pat. Nos. 3,401,922 issued Sept. 17, 1968, U.S. Pat. No. 3,373,982 issued Mar. 19, 1968 and U.S. Pat. No. 3,027,147 issued to Brakel, et al. on Mar. 27, 1962. These patents are each directed to grate systems for uniformly removing particulate matter from a cylindrical vessel.
As mentioned previously, it is very difficult in cylindrical vessels to uniformly distribute the treating fluids across the cross-section of the vessel since linear plenums which are typically used in vessels of rectangular cross-section do not uniformly distribute fluids across a circular cross-section. Accordingly, prior art cylindrical vessels have typically been inferior to rectangular vessels insofar as the application of treating fluids to the particulate matter.
Another prevalent problem in particle treating vessels resides in the fact that many times the treating fluids constitute gases which may be toxic or need to be confined for other reasons, and it is difficult to confine or eliminate the emission of such gases from a constant feed system where the particulate matter is fed into the top of a vessel.
It is to overcome the problems and shortcomings of the prior art that the present invention has been developed.